Ugghhh! It is absolutely horrible that he hurt the kids to get back at you.
My kids play on fall sports too so I can totally relate. They would be equally as devastated if they missed their last celebration and game. I am so sorry for you and them.
Could you possibly email or contact the team for a "final" end of season celebration at maybe a pizza place or local kid friendly restaurant or even host it at your house and have it a potluck? That might give your kids a chance to participate in the fun they missed.
Hugs to you. All I have to say is I believe in Karma, what comes around goes around.